/**
 * 求两个颜色之间的渐变值
 * @param {string} startColor 开始的颜色
 * @param {string} endColor 结束的颜色
 * @param {number} step 颜色等分的份额
 * */
function colorGradient(startColor = 'rgb(0, 0, 0)', endColor = 'rgb(255, 255, 255)', step = 10) {
  const startRGB = hexToRgb(startColor, false) // 转换为rgb数组模式
  const startR = startRGB[0]
  const startG = startRGB[1]
  const startB = startRGB[2]

  const endRGB = hexToRgb(endColor, false)
  const endR = endRGB[0]
  const endG = endRGB[1]
  const endB = endRGB[2]

  const sR = (endR - startR) / step // 总差值
  const sG = (endG - startG) / step
  const sB = (endB - startB) / step
  const colorArr = []
  for (let i = 0; i < step; i++) {
    // 计算每一步的hex值
    let hex = rgbToHex(`rgb(${Math.round((sR * i + startR))},${Math.round((sG * i + startG))},${Math.round((sB *
			i + startB))})`)
    // 确保第一个颜色值为startColor的值
    if (i === 0) hex = rgbToHex(startColor)
    // 确保最后一个颜色值为endColor的值
    if (i === step - 1) hex = rgbToHex(endColor)
    colorArr.push(hex)
  }
  return colorArr
}

// 将hex表示方式转换为rgb表示方式(这里返回rgb数组模式)
function hexToRgb(sColor, str = true) {
  const reg = /^#([0-9a-fA-f]{3}|[0-9a-fA-f]{6})$/
  sColor = String(sColor).toLowerCase()
  if (sColor && reg.test(sColor)) {
    if (sColor.length === 4) {
      let sColorNew = '#'
      for (let i = 1; i < 4; i += 1) {
        sColorNew += sColor.slice(i, i + 1).concat(sColor.slice(i, i + 1))
      }
      sColor = sColorNew
    }
    // 处理六位的颜色值
    const sColorChange = []
    for (let i = 1; i < 7; i += 2) {
      sColorChange.push(parseInt(`0x${sColor.slice(i, i + 2)}`))
    }
    if (!str) {
      return sColorChange
    }
    return `rgb(${sColorChange[0]},${sColorChange[1]},${sColorChange[2]})`
  } if (/^(rgb|RGB)/.test(sColor)) {
    const arr = sColor.replace(/(?:\(|\)|rgb|RGB)*/g, '').split(',')
    return arr.map((val) => Number(val))
  }
  return sColor
}

// 将rgb表示方式转换为hex表示方式
function rgbToHex(rgb) {
  const _this = rgb
  const reg = /^#([0-9a-fA-f]{3}|[0-9a-fA-f]{6})$/
  if (/^(rgb|RGB)/.test(_this)) {
    const aColor = _this.replace(/(?:\(|\)|rgb|RGB)*/g, '').split(',')
    let strHex = '#'
    for (let i = 0; i < aColor.length; i++) {
      let hex = Number(aColor[i]).toString(16)
      hex = String(hex).length == 1 ? `${0}${hex}` : hex // 保证每个rgb的值为2位
      if (hex === '0') {
        hex += hex
      }
      strHex += hex
    }
    if (strHex.length !== 7) {
      strHex = _this
    }
    return strHex
  } if (reg.test(_this)) {
    const aNum = _this.replace(/#/, '').split('')
    if (aNum.length === 6) {
      return _this
    } if (aNum.length === 3) {
      let numHex = '#'
      for (let i = 0; i < aNum.length; i += 1) {
        numHex += (aNum[i] + aNum[i])
      }
      return numHex
    }
  } else {
    return _this
  }
}

/**
* JS颜色十六进制转换为rgb或rgba,返回的格式为 rgba（255，255，255，0.5）字符串
* sHex为传入的十六进制的色值
* alpha为rgba的透明度
*/
function colorToRgba(color, alpha) {
  color = rgbToHex(color)
  // 十六进制颜色值的正则表达式
  const reg = /^#([0-9a-fA-f]{3}|[0-9a-fA-f]{6})$/
  /* 16进制颜色转为RGB格式 */
  let sColor = String(color).toLowerCase()
  if (sColor && reg.test(sColor)) {
    if (sColor.length === 4) {
      let sColorNew = '#'
      for (let i = 1; i < 4; i += 1) {
        sColorNew += sColor.slice(i, i + 1).concat(sColor.slice(i, i + 1))
      }
      sColor = sColorNew
    }
    // 处理六位的颜色值
    const sColorChange = []
    for (let i = 1; i < 7; i += 2) {
      sColorChange.push(parseInt(`0x${sColor.slice(i, i + 2)}`))
    }
    // return sColorChange.join(',')
    return `rgba(${sColorChange.join(',')},${alpha})`
  }

  return sColor
}

export {
  colorGradient,
  hexToRgb,
  rgbToHex,
  colorToRgba
}
